Combined treatment with cytoprotective agents and radiotherapy

60Coγ induction improves the protective effect of Acetobacter pasteurianus against ionizing radiation in mice

Exposure to ionizing radiation (IR) tends to cause serious health concerns. Thus, radioprotective agents are vital for the population exposed to radiation. As microorganisms have the advantages of fast reproduction and no geographical restrictions, direct microbe-based and environmental induction compounds are thriving radioprotectants resources. Oxidative system and oxidase in Acetobacter pasteurianus are unique and intriguing, the radioprotective effect of the cell-free extract from A. pasteurianus (APE) and ⁶⁰Coγ-treated extract (IRE) were comparatively investigated in the present study. The survival rate of A. pasteurianus with IRE addition was 149.1% in H₂O₂ damage test, while that with APE was only 10.4%. The viability of ⁶⁰Coγ-treated AML-12 cells was increased by 18.8% with IRE addition, yet APE showed no significant radioprotective effect. Moreover, in ⁶⁰Coγ-treated mice, IRE could significantly protect the white blood cell, improve the liver index, and attenuate the injuries of immune organs in mice. Administration of IRE significantly raised the activities of superoxide dismutase (SOD) and reduced the products of lipid peroxidation. These results clarified that gavage with APE and IRE presented notable antioxidant and radioprotective efficacy. A. pasteurianus showed appealing potential to be novel radioprotective bioagents and ⁶⁰Coγ treatment on microbe could be a new method for the development of better radioprotectant. KEY POINTS: • ⁶⁰Coγ induction could improve the radioprotective effect of APE. • IRE protected white blood cell in mice under IR. • IRE products have broad application prospects in radioprotection based on microbes.

The efficacy and safety of amifostine for the acute radiation syndrome

Introduction: A radiation countermeasure that can be used prior to radiation exposure to protect the population from the harmful effects of radiation exposure remains a major unmet medical need and is recognized as an important area for research. Despite substantial advances in the research and development for finding nontoxic, safe, and effective prophylactic countermeasures for the acute radiation syndrome (ARS), no such agent has been approved by the United States Food and Drug Administration (FDA). Area covered: Despite the progress made to improve the effectiveness of amifostine as a radioprotector for ARS, none of the strategies have resolved the issue of its toxicity/side effects. Thus, the FDA has approved amifostine for limited clinical indications, but not for non-clinical uses. This article reviews recent strategies and progress that have been made to move forward this potentially useful countermeasure for ARS. Expert opinion: Although the recent investigations have been promising for fielding safe and effective radiation countermeasures, additional work is needed to improve and advance drug design and delivery strategies to get FDA approval for broadened, non-clinical use of amifostine during a radiological/nuclear scenario.

A seleno-hormetine protects bone marrow hematopoietic cells against ionizing radiation-induced toxicities

2,2'-diselenyldibenzoic acid (DSBA) is a chemical probe produced to explore the pharmacological properties of diphenyldiselenide-derived agents with seleno-hormetic activity undergoing preclinical development. The present study was designed to verify in vivo the drug's properties and to determine mechanistically how these may mediate the protection of tissues against stress conditions, exemplified by ionizing radiation induced damage in mouse bone marrow. In murine bone marrow hematopoietic cells, the drug initiated the activation of the Nrf2 transcription factor resulting in enhanced expression of downstream stress response genes. This type of response was confirmed in human liver cells and included enhanced expression of glutathione S-transferases (GST), important in the metabolism and pharmacological function of seleno-compounds. In C57 BL/6 mice, DSBA prevented the suppression of bone marrow hematopoietic cells caused by ionizing radiation exposure. Such in vivo prevention effects were associated with Nrf2 pathway activation in both bone marrow cells and liver tissue. These findings demonstrated for the first time the pharmacological properties of DSBA in vivo, suggesting a practical application for this type of Se-hormetic molecules as a radioprotective and/or prevention agents in cancer treatments.

Expanding the therapeutic index of radiation therapy by normal tissue protection

Normal tissue damages induced by radiation therapy remain dose-limiting factors in radiation oncology and this is still true despite recent advances in treatment planning and delivery of image-guided radiation therapy. Additionally, as the number of long-term cancer survivors increases, unacceptable complications emerge and dramatically reduce the patients' quality of life. This means that patients and clinicians expect discovery of new options for the therapeutic management of radiation-induced complications. Over the past four decades, research has enhanced our understanding of the pathophysiological, cellular and molecular processes governing normal tissue toxicity. Those processes are complex and involve the cross-talk between the various cells of a tissue, including fibroblasts, endothelial, immune and epithelial cells as well as soluble paracrine factors including growth factors and proteases. We will review the translatable pharmacological approaches that have been developed to prevent, mitigate, or reverse radiation injuries based upon the targeting of cellular and signalling pathways. We will summarize the different steps of the research strategy, from the definition of initial biological hypotheses to preclinical studies and clinical translation. We will also see how novel research and therapeutic hypotheses emerge along the way as well as briefly highlight innovative approaches based upon novel radiotherapy delivery procedures.

Combining Pharmacological Countermeasures to Attenuate the Acute Radiation Syndrome-A Concise Review

The goal of combined pharmacological approaches in the treatment of the acute radiation syndrome (ARS) is to obtain an effective therapy producing a minimum of undesirable side effects. This review summarizes important data from studies evaluating the efficacy of combining radioprotective agents developed for administration prior to irradiation and therapeutic agents administered in a post-irradiation treatment regimen. Many of the evaluated results show additivity, or even synergism, of the combined treatments in comparison with the effects of the individual component administrations. It can be deduced from these findings that the research in which combined treatments with radioprotectors/radiomitigators are explored, tested, and evaluated is well-founded. The requirement for studies highly emphasizing the need to minimize undesirable side effects of the radioprotective/radiomitigating therapies is stressed.

Radioprotector WR-2721 and mitigating peptidoglycan synergistically promote mouse survival through the amelioration of intestinal and bone marrow damage

The identification of an agent effective for the treatment of intestinal and bone marrow injury following radiation exposure remains a major issue in radiological medicine. In this study, we evaluated the therapeutic impact of single agent or combination treatments with 2-(3-aminopropylamino) ethylsulphanyl phosphonic acid (WR-2721) and peptidoglycan (PGN, a toll-like receptor 2 (TLR-2) agonist) on radiation-induced injury of the intestine and bone marrow in lethally irradiated male C57BL/6 mice. A dose of 3 mg of WR-2721 per mouse (167 mg/kg, intraperitoneally) was given 30 min before irradiation, and 30 μg of PGN per mouse (1.7 mg/kg) was injected intraperitoneally 24 h after 10 Gy irradiation. Bone marrow cluster of differentiation (CD)45(+) and CD34(+) markers of multiple haematopoietic lineages, number of granulocyte-erythroid-macrophage-megakaryocyte (GEMM) progenitor colonies, bone marrow histopathology, leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) expression in the intestines, xylose absorption and intestinal histopathology were all assessed at various time-points after irradiation. Furthermore, nuclear factor kappa B (NF-κB) p65 protein in the ileum was stained by immunofluorescent labelling. PGN-treated irradiated mice showed an increase in CD45(+)CD34(+) cells compared with untreated mice 1.25 days after 10 Gy ionizing radiation (IR) (P < 0.05). Furthermore, combined PGN and WR-2721 treatment had an obviously synergistic radio-protective effect in nucleated cells in the bone marrow, including GEMM progenitors and CD45(+)CD34(+) cells 4 days after 10 Gy IR. Single agent PGN or WR-2721 treatment after 10 Gy IR clearly increased Lgr5-positive pit cells (P < 0.05) and xylose absorption (P < 0.05). However only PGN and WR-2721 combination treatment markedly increased villus height (P < 0.05), number of crypts (P < 0.05) and whole-body weights after 10 Gy whole-body irradiation (WBI). The NF-κB p65 subunit was translocated to the nucleus, and phosphate-IκBα (Ser32/Ser36) was detected after stimulation with either PGN or WR-2721, which indicates that these two agents act synergistically through the activation of the NF-κB pathway. Administration of PGN in combination with WR-2721 was demonstrated to have a synergistic effect on the increase in haematopoietic cells and intestinal reconstitution, as well as improved survival in lethally irradiated mice, but resulted in some degree of an immune disorder.

Management of normal tissue toxicity associated with chemoradiation (primary skin, esophagus, and lung)

Nearly one quarter of patients with lung cancer present with locally advanced disease where concurrent chemoradiotherapy is the current standard of care for patients with good performance status. Cisplatin-based concurrent chemoradiotherapy consistently showed an improvement in survival compared with sequential chemoradiotherapy, at the expense of an increase in the toxicity profile. Over the past decades, several encouraging biomarkers such as transforming growth factor-beta and radioprotective agents such as amifostine were studied but without reaching approval for patient care. We reviewed the prevalence and risk factors for different adverse effects associated with the combined chemoradiotherapy modality, especially dermatitis, mucositis, esophagitis, and pneumonitis. These adverse effects can further be divided into acute, subacute, and chronic. Dermatitis is usually rare and responds well to topical steroids and usual skin care. Acute esophagitis occurs in 30% of patients and is treated with proton pump inhibitors, promotility agents, local anesthetic, and dietary changes. Radiation pneumonitis is a subacute complication seen in 15% of patients and is usually managed with steroids. Chronic adverse effects such as radiation fibrosis and esophageal stricture occur approximately 6 months after completion of radiation therapy and are usually permanent. In this review, complications of chemoradiotherapy for patients with locally advanced lung cancer are delineated, and approaches to their management are described. Given that treatment interruption is associated with a worse outcome, patients are aggressively treated with a curative intent. Therefore, planning for treatment adverse effects improves patient tolerance, compliance, and outcome.

Antioxidant and antigenotoxic role of recombinant human erythropoeitin against alkylating agents: Cisplatin and mitomycin C in cultured Vero cells

Cisplatin (CDDP) and mitomycin C (MMC), two alkylating agents used against various solid tumours, are a common source of acute kidney injury. Thus, strategies for minimizing CDDP and MMC toxicity are of a clinical interest. In this study, we aimed to investigate the protective role of recombinant human erythropoietin (rhEPO) against oxidative stress and genotoxicity induced by CDDP and MMC in cultured Vero cells. Three types of treatments were performed: (i) cells were treated with rhEPO 24 h before exposure to CDDP/MMC (pre-treatment), (ii) cells were treated with rhEPO and CDDP/MMC simultaneously (co-treatment), (iii) cells were treated with rhEPO 24 h after exposure to CDDP/MMC (post-treatment). Our results showed that rhEPO decreased the reactive oxygen species levels, the malondialdehyde levels and ameliorated glutathione (reduced and oxidized glutathione) modulation induced by CDDP and MMC in cultured Vero cells. Furthermore, rhEPO administration prevented alkylating agents-induced DNA damage accessed by comet test. Altogether, our results suggested a protective role of rhEPO, against CDDP- and MMC-induced oxidative stress and genotoxicity, especially in pre-treatment condition.

ROS-scavenger and radioprotective efficacy of the new PrC-210 aminothiol

To identify new aminothiol radioprotectors that are active when applied topically and have fewer side effects when administered systemically, a new family of aminothiol radioprotectors was designed and synthesized. Three key elements in the aminothiol design were, (1) small size for efficient transmembrane diffusion, (2) positive charged amines in alkyl backbone for strong ionic interaction with DNA backbone, and (3) a perpendicular, alkyl side-chain with a terminal thiol that is projected away from the DNA backbone to enable reactive oxygen species scavenging around DNA. Several in vitro assays were used to characterize the prototype aminothiol, PrC-210, for efficacy: protection against reactive oxygen species-induced plasmid DNA nicking, mass spectrometry to detect aminothiol-reactive oxygen species by-products, S. typhimurium mutagenesis, human cell growth inhibition, Western blot for p21 expression, and FACS analysis. Additionally, two in vivo assays were used to assess radioprotective efficacy; a Sprague-Dawley rat dorsal skin radiodermatitis assay was developed to screen for aminothiol efficacy when topically applied, and ICR mouse survival was scored after systemic PrC-210 administration and whole-body radiation. PrC-210 efficiently scavenged reactive oxygen species and completely protected supercoiled plasmid DNA against reactive oxygen species-induced damage. Neither PrC-210 nor its analog PrC-211 were bacterial mutagens. In cell culture, PrC-210 application to diploid human fibroblasts showed: (1) inhibition of cell growth with an IC(70) of 4.1 mM, (2) induced levels of p21 expression, and (3) a G(1)/S-cell cycle block that was reversed after washout of PrC-210-containing medium. In rodents, PrC-210 was an effective radioprotector showing: (1) complete prevention of Grade 2-3 radiodermatitis when applied topically (370 mM in ethanol:propylene glycol:water solution) prior to skin irradiation, (2) complete prevention of Grade 2-3 radiodermatitis when administered by i.p. injection (200 μg/g of body weight) before skin irradiation, (3) 100% survival of mice from an otherwise 100% lethal dose of whole-body radiation (8.75 Gy) when administered by i.p. injection (252 μg/g of body weight = 0.5 × maximum tolerated dose) before irradiation, and (4) a dose reduction factor of 1.6, the same as amifostine. These data suggest that the PrC-210 aminothiol is a plausible candidate for drug development as a human pre-exposure radioprotector.

Reduction of renal uptake of radiolabeled octreotate by amifostine coadministration

Megalin-mediated renal retention of radiolabeled somatostatin analogs may lead to nephrotoxicity during peptide receptor radionuclide therapy (PRRT). The cytoprotective agent amifostine protected rats from long-term nephrotoxicity after PRRT with (177)Lu-DOTA,Tyr(3)-octreotate. This study describes the direct effect of amifostine on kidney and tumor uptake of (111)In-DOTA,Tyr(3)-octreotate.

METHODS

In vivo biodistribution studies were performed using CA20948 tumor-bearing rats, with or without amifostine coadministration, via several routes. In vitro uptake was studied in somatostatin receptor-expressing CA20948 and megalin or cubilin receptor-expressing BN-16 cells, in the absence or presence of amifostine or its active metabolite WR-1065.

RESULTS

Coadministration of amifostine decreased renal uptake of radiolabeled octreotate in vivo, whereas tumor uptake was not affected. In agreement, amifostine and WR-1065 coincubation reduced uptake in BN-16 but not in CA20948 cells.

CONCLUSION

Amifostine may provide renal protection during PRRT using somatostatin analogs, both by mitigation of radiation damage and the currently observed reduction of absorbed kidney radiation dose.

A new orally active, aminothiol radioprotector-free of nausea and hypotension side effects at its highest radioprotective doses

PURPOSE

A new aminothiol, PrC-210, was tested for orally conferred radioprotection (rats, mice; 9.0 Gy whole-body, which was otherwise lethal to 100% of the animals) and presence of the debilitating side effects (nausea/vomiting, hypotension/fainting) that restrict use of the current aminothiol, amifostine (Ethyol, WR-2721).

METHODS AND MATERIALS

PrC-210 in water was administered to rats and mice at times before irradiation, and percent-survival was recorded for 60 days. Subcutaneous (SC) amifostine (positive control) or SC PrC-210 was administered to ferrets (Mustela putorius furo) and retching/emesis responses were recorded. Intraperitoneal amifostine (positive control) or PrC-210 was administered to arterial cannulated rats to score drug-induced hypotension.

RESULTS

Oral PrC-210 conferred 100% survival in rat and mouse models against an otherwise 100% lethal whole-body radiation dose (9.0 Gy). Oral PrC-210, administered by gavage 30-90 min before irradiation, conferred a broad window of radioprotection. The comparison of PrC-210 and amifostine side effects was striking because there was no retching or emesis in 10 ferrets treated with PrC-210 and no induced hypotension in arterial cannulated rats treated with PrC-210. The tested PrC-210 doses were the ferret and rat equivalent doses of the 0.5 maximum tolerated dose (MTD) PrC-210 dose in mice. The human equivalent of this mouse 0.5 MTD PrC-210 dose would likely be the highest PrC-210 dose used in humans. By comparison, the mouse 0.5 MTD amifostine dose, 400 μg/g body weight (equivalent to the human amifostine dose of 910 mg/m(2)), when tested at equivalent ferret and rat doses in the above models produced 100% retching/vomiting in ferrets and 100% incidence of significant, progressive hypotension in rats.

CONCLUSIONS

The PrC-210 aminothiol, with no detectable nausea/vomiting or hypotension side effects in these preclinical models, is a logical candidate for human drug development to use in healthy humans in a wide variety of radioprotection settings, including medical radiation, space travel, and nuclear accidents.

Protective effect of recombinant human erythropoeitin against cisplatin cytotoxicity and genotoxicity in cultured Vero cells

Cisplatin is an effective agent against various solid tumors. Despite its effectiveness, the dose of cisplatin that can be administered is limited by its nephrotoxicity. Therefore, strategies for minimising the toxicity of cisplatin are of a clinical interest. The aim of this study was to investigate the protective effect of recombinant human erythropoietin (rhEPO) against the cytotoxicity and apoptosis induced by cisplatin in cultured Vero cells. Three types of treatments were performed: (i) cells were treated with rhEPO 24 h before exposure to cisplatin (pre-treatment), (ii) cells were treated with rhEPO and cisplatin simultaneously (co-treatment), (iii) cells were treated with rhEPO 24 h after exposure to cisplatin (post-treatment). Our results showed that rhEPO reduced cisplatin-induced cell mortality. Besides, rhEPO administration prevented cisplatin-induced DNA damage. Furthermore, rhEPO decreased the caspase-3 activity and pro-apoptotic factors levels (p53 and Bax) induced by cisplatin. It increased also the expression of the anti-apoptotic factor Bcl2 in Vero cells. Altogether, our results suggest a protective action of rhEPO against cisplatin cytotoxicity and genotoxicity via an anti-apoptotic process. The most protective effect was observed with rhEPO when it was administrated 24 h before cisplatin treatment.

Magnetic resonance imaging of organic contrast agents in mice: capturing the whole-body redox landscape

Nitroxides are a class of stable free radicals that have several biomedical applications including radioprotection and noninvasive assessment of tissue redox status. For both of these applications, it is necessary to understand the in vivo biodistribution and reduction of nitroxides. In this study, magnetic resonance imaging was used to compare tissue accumulation (concentration) and reduction of two commonly studied nitroxides: the piperidine nitroxide Tempol and the pyrrolidine nitroxide 3-CP. It was found that 3-CP was reduced 3 to 11 times slower (depending on the tissue) than Tempol in vivo and that maximum tissue concentration varies substantially between tissues (0.6-7.2mM). For a given tissue, the maximum concentration usually did not vary between the two nitroxides. Furthermore, using electron paramagnetic resonance spectroscopy, we showed that the nitroxide reduction rate depends only weakly on cellular pO(2) in the oxygen range expected in vivo. These observations, taken with the marked variation in nitroxide reduction rates observed between tissues, suggest that tissue pO(2) is not a major determinant of the nitroxide reduction rate in vivo. For the purpose of redox imaging, 3-CP was shown to be an optimal choice based on the achievable concentrations and bioreduction observed in vivo.

Amifostine modulates radio-induced apoptosis of peripheral blood lymphocytes in head and neck cancer patients

Head and neck cancer is treated mainly with surgery and radiotherapy. Xerostomia and mucositis are common adverse effects of radiation therapy. One of the strategies aimed at decreasing radiation toxicity is the use of radioprotective agents, such as amifostine. We previously reported that radio induced apoptosis of peripheral blood lymphocytes was statistically associated with normal tissue toxicity in the form of severe xerostomia. The aim of the present study was to explore the effects of amifostine on the radiation-induced apoptosis of peripheral blood lymphocytes from patients suffering head and neck cancer. Eighteen consecutive patients with squamous cell carcinoma of the head and neck were included in the study. Peripheral blood lymphocytes were isolated before and after the treatment with amifostine. Then, cells were irradiated at 0, 1, 2 and 8 Gy during 24 hours. Apoptosis was measured by flow cytometry using annexin V/propidium iodide. As expected, radio-induced apoptosis values fitted to a semi logarithmic equation as follows: RIA = β ln(Gy) + α. The administration of amifostine prior to radiation therapy modulates radio-induced apoptosis of peripheral blood lymphocytes: 13.68 vs. 13.37 (P = 0.027), 19.11 vs. 17.64 (P = 0.001) and 30.70 vs. 28.84 (P = 0.001), before and after the administration of the drug for 1, 2 and 8 Gy respectively. α and β decreased significantly after the administration of the drug: 13.58 vs. 12.99 (P = 0.009) and 8.21 vs. 7.53 (P = 0.017), respectively. Our results provide new information about the biological actions of amifostine in vivo.

Randomized phase II exploratory study of prophylactic amifostine in cancer patients who receive radical radiotherapy to the pelvis

BACKGROUND

This study aimed to investigate the efficacy of prophylactic amifostine in reducing the risk of severe radiation colitis in cancer patients receiving radical radiotherapy to the pelvis.

METHODS

Patients with pelvic tumours referred for radical radiotherapy who consented participation in this trial, were randomly assigned to receive daily amifostine (A) (subcutaneously, 500 mg flat dose) before radiotherapy or radiotherapy alone (R). Sigmoidoscopy and blinded biopsies were scheduled to conduct prior to initiation and following completion of radiotherapy and again 6 to 9 months later. Radiation colitis was assessed by clinical, endoscopic and histolopathological criteria.

RESULTS

A total 44 patients were enrolled in this trial, the majority with rectal (20 patients) and cervical cancer (12 patients) and were assigned 23 in R arm and 21 in the A arm. In total 119 sigmoidoscopies were performed and 18 patients (18/44, 40.9%) were diagnosed with radiation colitis (15 grade 1 and 2, and 3 grade 3 and 4). Of them, 6 patients belonged to the A group (6/21, 28.6%) and 12 to the R group (12/23, 52.2%). Acute and grade IV radiation colitis was only developed in four patients (17.4%) in the R group. Amifostine side effects were mild. Amifostine treated patients were less likely to develop histologically detectable mucosal lesions, which indicate protection from acute mucosal injury.

CONCLUSIONS

Amifostine given subcutaneously can lower the risk of acute severe radiation colitis in patients who receive radical radiotherapy to pelvic tumors.

Prediction of clinical toxicity in locally advanced head and neck cancer patients by radio-induced apoptosis in peripheral blood lymphocytes (PBLs)

Head and neck cancer is treated mainly by surgery and radiotherapy. Normal tissue toxicity due to x-ray exposure is a limiting factor for treatment success. Many efforts have been employed to develop predictive tests applied to clinical practice. Determination of lymphocyte radio-sensitivity by radio-induced apoptosis arises as a possible method to predict tissue toxicity due to radiotherapy. The aim of the present study was to analyze radio-induced apoptosis of peripheral blood lymphocytes in head and neck cancer patients and to explore their role in predicting radiation induced toxicity. Seventy nine consecutive patients suffering from head and neck cancer, diagnosed and treated in our institution, were included in the study. Toxicity was evaluated using the Radiation Therapy Oncology Group scale. Peripheral blood lymphocytes were isolated and irradiated at 0, 1, 2 and 8 Gy during 24 hours. Apoptosis was measured by flow cytometry using annexin V/propidium iodide. Lymphocytes were marked with CD45 APC-conjugated monoclonal antibody. Radiation-induced apoptosis increased in order to radiation dose and fitted to a semi logarithmic model defined by two constants: α and β. α, as the origin of the curve in the Y axis determining the percentage of spontaneous cell death, and β, as the slope of the curve determining the percentage of cell death induced at a determined radiation dose, were obtained. β value was statistically associated to normal tissue toxicity in terms of severe xerostomia, as higher levels of apoptosis were observed in patients with low toxicity (p = 0.035; Exp(B) 0.224, I.C.95% (0.060-0.904)). These data agree with our previous results and suggest that it is possible to estimate the radiosensitivity of peripheral blood lymphocytes from patients determining the radiation induced apoptosis with annexin V/propidium iodide staining. β values observed define an individual radiosensitivity profile that could predict late toxicity due to radiotherapy in locally advanced head and neck cancer patients. Anyhow, prospective studies with different cancer types and higher number of patients are needed to validate these results.